A substantial part of the big green area below the bandstand - the main area - has been fenced off and grass removed. It looks like they're going to build something there.
If this is really so, I take back everything I said before about trusting the Horniman to do the right thing, and am with seeformiles and roz. You can't build on that area of green. There are plenty of educational buildings etc on the top part. That lower part of the park should be left in peace. Children need green space to run around in quite as much, if not more, than being crammed full of education every time they breathe in.
Perhaps they're re-turfing it or something? One can but hope.